Human exhaled breath analysis

Objective: To review the fast-developing topic of assessment of exhaled breath components to improve the diagnosis and monitoring of respiratory and systemic diseases.

Data sources: Review of the literature available in monographs and journals.

Study selection: Articles and overviews on the broad spectrum of existing experimental and routinely applied methods to assess different aspects of human exhaled breath analysis were selected for presentation in this review.

Results: Exhaled breath constitutes more than 3,500 components, the bulk of which are volatile organic compounds in miniature quantities. Many of these characterize the functioning of the organism as a whole (systemic biomarkers), but some are related to processes taking place in the respiratory system and the airways in particular (lung biomarkers). Assessment of lung biomarkers has proven useful in airway inflammatory diseases. It involves direct measurement of gases such as nitric oxide and inflammatory indicators in exhaled breath condensate such as oxidative stress markers (eg, hydrogen peroxide and isoprostanes), nitric oxide derivatives (eg, nitrate and nitrates), arachidonic acid metabolites (eg, prostanoids, leukotrienes, and epoxides), adenosine, and cytokines. Integral approaches have also been suggested, such as exhaled breath temperature measurement and devices of the "electronic nose" type, which enable the capture of approaches have also been suggested, such as exhaled breath temperature measurementexhaled molecular fingerprints (breath prints). Technical factors related to standardization of the different techniques need to be resolved to reach the stage of routine applicability.

Conclusions: Examination of exhaled breath has the potential to change the existing routine approaches in human medicine. The rapidly developing new analytical and computer technologies along with novel, unorthodox ideas are prerequisites for future advances in this field.